Thermal element



P 1962 s. G. ESKIN 3,053,092

THERMAL ELEMENT Filed June 12, 1956 hrs .27 2272-" 61444054 6. fsK/A/ ...L I F, vi-

United States Patent 3,053,092 THERMAL ELEMENT Samuel G. Eskin, Chicago, Ill., assignor, by mesne assignments, to Antioch College, Yellow Spring, Ohio, a corporation of Ohio Filed June 12, 1956, Ser. No. 590,910 5 Claims. (Cl. 73-3683) This invention relates to improvements in thermal elements and more particularly relates to thermal responsive power generating elements for actuating control devices in accordance with changes in temperature to which the elements are subjected, and commonly referred to as wax or power types of thermal elements.

Heretofore, various types of thermal responsive power generating elements have been used in which the power generating material is a fusible organic crystalline substance having a fusion point within the intended operating range of the thermal element and having a finely divided heat conductive material, solid in the operating range of the thermal element, dispersed through the body of the crystalline substance to conduct heat through the mass of the crystalline substance, and held from settling out of the crystalline substance by a binder.

One form taken by such thermal elements is a relatively large diameter cylindrical casing having a shallow chamber carrying the fusible thermally expansible material in the form of a pellet or disk, to react against a thin metal flexible disk, which closes the casing. While such elements are generally satisfactory, for a given initial temperature diiference a relatively long period of time is required to obtain the desired movement of the flexible disk, due to the fact that the fusible material acts on the entire surface of the disk.

A principal object of the invention is to remedy the foregoing difficulties by providing a motion amplifier or accelerator, confining the action of a portion of the thermally expansible material of a thermal element to a small area of the diaphragm, forming the power member of the thermal element, and thus increasing movement of the power member in a given unit of time over former thermal elements.

A further object of the invention is to provide a novel and improved form of thermal element especially adapted for clamp-on applications in which the action of the thermally expansible material against the power member of the thermal element is accelerated by afunnel-like motion amplifier opening at its small end toward the power member of the thermal element and imbedded in the fusible thermally expansible material, to confine a portion of the thermally expansible material to act on the power member upon changes in temperature, within the range of fusion of the thermally expansi'ble material.

Another object of the invention is to provide a thermally expansible pellet in the form of a solid mass of fusible material having a motion amplifier or accelerator compacted therein.

Still another object of the invention is to provide a fusible pellet for a thermal element of the power type, in which the motion of expansible movement of the fusible material is accelerated by a motion amplifier in the general form of a funnel imbedded in the pellet with its small diameter end adjacent the power member of the thermal element.

It is a further and important object of the invention to provide a thermal responsive power generating element having improved motion transmission characteristics with less lag in response to thermal changes to which the thermal element may be subjected.

These and other objects of the invention will appear from time to time as the following specification proceeds "ice and with reference to the accompanying drawings wherein:

FIGURE 1 is a cross-sectional view taken through a thermal element and pellet constructed in accordance with the present invention; and

FIGURE 2 is a cross-sectional view illustrating a modified form in which the invention may be embodied.

In the embodiment of the invention illustrated in the drawing, I have shown a container or casing 10, which may be generally cylindrical in form. The casing has a bottom 11, an open top and a generally cylindrical inner wall 12, the inner margin of which wall with the bottom 11 defines a chamber for containing a fusible thermally responsive material, which may be in the form of a disklike pellet 13. The pellet 13 is contained within the casing by a relatively thin, flat tempered spring steel selfreturning metal disk or diaphragm 15 engaging a shouldered portion 16 of the wall of the casing, and retained thereto by the forming or spinning of a reduced crosssectional area wall portion 17 of the casing thereover into engagement with an annular sealing member or gasket 19, extending around the outer marginal portion of the disk 15.

The means for accelerating the movement of the disk upon an increase in temperature is shown as being a rigid frusto-conical or funnel-like amplifier 21, which may be compacted in the pellet 13 so as to have its small diameter open end portion adjacent the disk 15.

The motion amplifier 21 is made from a gauge of metal considerably thicker than that of the disk or diaphragm 15 and is wider at its bottom than its top to provide a rigid frusto-conical wall confining the fusible thermal responsive material to act initially on a small area of the disk 15 when heat is supplied to the bottom 11 of the thermal element. The open small diameter top of the amplifier may come in contact with the under surface of the disk 15 when said disk is in its flat unstressed condition. Spaced stops 23 are shown as extending upwardly from the outer surface of the motion amplifier 21 to engage the disk 15 outwardly of its center.

The pellet 13 may be formed from a fusible thermally expansible material which may be a wax containing a powdered metal heat conductor and a binder as shown and described in the Vernet Patent No. 2,259,846. The wax may be selected for its melting temperature, a paraffine wax being selected for a low operating range such as 92 to 102 F. and a microcrystalline wax being selected for a high temperature range of operation such as from a to F. The powdered metal heat conductor may preferably be copper, although aluminum, carbon, graphite and antimony and combinations of these metals with each other or with copper are suitable heat conductors. The binder may be an unsaturated hydrocarbon polymer or a vinyl polymer as in the aforementioned Patent No. 2,259,846.

The pellet may also be made from a wax alone for low melting point operation, the type of wax selected depending upon the temperature range of operation of the thermal element, as previously mentioned. In the present invention, a wax alone is particularly suitable for low temperature operation of the thermal element since the motion of the wax as it fuses is accelerated by the motion amplifier 21, which confines and thus speeds up the action of the wax.

The pellet 13 may be formed, as shown and described in the Vernet Patent No. 2,259,846, so the process of pelletizing need not herein be shown or described in detail. In pelletizing, the funnel-like motion amplifier is inserted in the wax and is compacted therein during the pelletizing process. The funnel-like motion amplifier 21 and the wax copper compound, therefore, form a unitary pellet which is assembled in the casing 10 with the small diameter open end portion of the motion amplifier in juxtaposition to the flexible disk or diaphragm 15.

In the form of the invention illustrated in FIGURE 2, Lhave. shown a funnel-like motion amplifier 25 irnbedded in 'a pellet 26 of a thermal element 27 of a type, such as is shown and described. in the Vernet Patent No. 2,368,- 181, dated January 30, 1945.

' In this form of the invention, a rubber diaphragm 29 closes acasing 30 for the pellet 26 and has a stepped pliig 31. depending therefrom and serving to protect the diaphragm. The stepped plug 31 has a large diameter portion 32 which ab uts the upper end of the motion amplifier 25, and a small diameter portion 33 of which extends within a neck 35 of the motion amplifier 25, to herdirectly acted upon by the fusible thermally expansible', material within the motion amplifier, to accelerate extensible travel of a piston 36 from a cylinder 37 of the thermal element.

"Ihe funnel-like. amplifier 25 is preferably imbedded within the pellet 26 during the operation of pelletizing the. pellet as previously described, and may be made fromja non-deformable material which may be steel or copper, or any other suitable material.

The funnel-like motion amplifier may also be made of a material which is non-conductive of heat, where it is desired to speed up the expansion of the thermally expansible material Within the motion amplifier and retard the expansion of the thermally expansible material outside. of the motion amplifier, to initially give a fast action. to extensible movement of the piston 36 from the cylinder 37.

It may be seen. from the foregoing, that I have pro vided a simple means for accelerating the movement of the. power member of. a thermal element by confining the fusible thermally expansible material of the thermal element to act on a small area of the disk or diaphragm of the thermal element.

It may further be seen that this may be attained by the. use of a solid fusible thermally expansible pellet having a funnel-like motion amplifier im-bedded therein, asa part thereof, which may be placed in the casing of the, thermal element as in the standard forms of the thermalelements, to accelerate movement of the diaphragm or power member of the thermal element with an attendant reduction in size of the fusible thermally expansibl e pellet required, over the pellets formerly requiredifor the same amount of movement.

It; should here be. understood that the funnel-like motion amplifier does not increase the amount of motion ayailable from the thermal element for a given tempera ture change, but does increase the motion in a given unit ftirne and that this is the intended construction of the term amplifier as used. herein.

It will be understood that various modifications and variations of-the present invention may be eifected without departing from thepspiritand scope of the novel concents thereof.

I claim as my invention: 1. Ina thermalresponsive element, a casing, a flexible .4 diaphragm closing the open end of said casing, a fusible thermally expansi'ble material contained within said casing by said diaphragm and having a funnel-like motion amplifier embedded therein having a small diameter open end portion facing said diaphragm, and a plug extending from said diaphragm into abutting engagement with the small diameter end of said motion amplifier.

2. In a thermal responsive element, a casing having an open end, a flexible diaphragm closing the open end of said casing, a fusible thermally expansible material contained within said casing by said diaphragm and having a funnel-like motion amplifier embedded therein having a small diameter open end portion facing said diaphragm, and astepped plug extending from said diaphragm having a large diameter portion engageable with the small diameter end portion of said motion amplifier, and having a small diameter portion extending within said motion amplifier.

3. In a thermal responsive element, an open ended casing containing a thermally expansible material, a movable wall closing the open end of said casing, and a hollow member disposed in a fixed position within said casing and havingone end engageable with at least a portion of said movable wall, the cross-sectional area of the interior of said hollow member decreasing in a. direc tion perpendicular to and toward said movable Wall.

4. In a thermal responsive element, a casing having a rigid end wall at one end, a fusible thermally expansible material within said casing, a flexible diaphragm closing the other end of said casing and retaining the fusible thermally expansible material therein, and a hollow generally cone shaped member within said casing extending between said diaphragm and said one end wall of said casing and being surrounded by and filled with said fusible: thermally expansible material therein, and a hollow member within said casing opening to said diaphragm being surrounded by and filled with said fusible thermally expansible material, the cross sectional area of the interior of said hollow member decreasing in a direction perpendicular to and toward said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS 1,359,107 Roesch Nov. 16, 1920 1,907,869 Raney May 9, 1933 2,115,502 Vernet Apr. 26, 1938 2,259,846 Vernet et a1 Oct. 21, 1941 2,368,181 Vernet Jan. 30, 1945 2,453,851 Miller' Nov. 16, 1948 2,510,473 Jensen June 6, 1950 2,736,604 Albright Feb. 28, 1956 FOREIGN PATENTS 327,978 Great Britain Apr. 14, 1929 

